With the fast development of display technology, touch screen panels have gradually become popular in life. At present, touch screen panels may be classified into resistive type, capacitive type, infrared ray type and surface acoustic wave type depending on their operating principles. Capacitive touch screen panels are widely applied in industry since they can realize true multi-point control and high sensitivity.
Capacitive touch screen panels may be classified into add-on touch screen panels, on-cell touch screen panels and in-cell touch screen panels according to their configuration structures. For add-on touch screen panels, the touch screen panel and display screen need to be produced separately and then attached together to form a liquid crystal display with touch function. Add-on touch screen panels suffer disadvantages of high manufacturing costs, low light transmittance ratio and great module thickness. For an in-cell touch screen panel, the touch electrodes of touch screen panel are embedded in the liquid crystal display so as to reduce the entire thickness of a module and greatly reduce manufacturing costs of the touch screen panel. Therefore, in-cell touch screen panels have become attractive for panel manufacturers.
At present, conventional capacitive in-cell touch screen panels use two parallel electrodes to form a capacitor. When an operator touches the touch screen panel, capacitance at an intersection of two electrodes varies, and therefore it is possible to determine the location where the operator touches the screen from the variance in the capacitance.
FIG. 1A is a top view of a pixel unit in a conventional capacitive in-cell touch screen panel, FIG. 1B is an enlarged schematic diagram of a pixel unit on right side of FIG. 1A, and FIG. 2 is a sectional view along line A-A′ in FIG. 1B.
The array substrate 10 of the conventional touch screen panel includes a plurality of gate lines 50, a plurality of data lines 60, a plurality of second thin film transistors 20, a plurality of first transistors 40, touch sensing lines 30, touch scanning lines 80 and sensing electrodes 31 formed on a base substrate 11. Extending parts 301 electrically connected with the touch sensing lines 30 are on a same layer as the sensing electrodes 31, and the extending parts 301 of the touch sensing lines 30 are disposed opposite the side surface of the sensing electrodes 31 to form coupling capacitors. The sensing electrode 31 is connected with a source electrode 43 of the first transistor 40, and the touch scanning line 80 is connected with a gate electrode 41 and a drain electrode 44 of the first transistor 40. When an operator touches the touch screen panel, the touch influences capacitance between the touch sensing line 30 and the sensing electrode 31 to make the coupling capacitance at the touch location different from that at other locations. The touch screen panel determines the location where the operator touches the touch screen panel according to the received location of coupling capacitor in which capacitance varies.
Defects with the above-mentioned conventional touch screen panels lie in that, as illustrated in FIG. 1B, the coupling capacitors formed by extending parts of touch sensing lines and sensing electrodes parallel to each other in the same plane occupy large areas of the detection units, and since the coupling capacitors are located in non-display areas of the display screen, thereby reducing aperture ratio of the touch screen panel and influencing brightness of the display device.